Chapter 31: Escape and Salvage Arrangements
31. 1 Escape Arrangements
1. In 1908 approval was given to fit C12-16 with 'airlocks' or 'air-traps' as they were sometimes called. They were built of steel skirting projecting from the pressure hull over on the port side abreast the torpedo hatch about 10ft 6in long, 2ft 6in deep at the forward end and 3ft 6in deep at the after end. The enclosed space was divided into three airlocks. A fourth airlock was fitted on the starboard side. Sixteen diving helmets were stowed in these airlocks, that is one helmet for each man in the complement.
The escape route was through the torpedo hatch. This hatch was a flat rectangular plate about 6ft x 2ft secured by six clips. Three l½in x ¼in iron bars were fitted to the inside of the hatch and their lower ends to a wooden iron-cored bar. The casing top hinged cover was connected to the torpedo hatch by a wire link to pull the cover closed when the torpedo hatch closed. A number of hands on the wooden bar could push open the hatch-the pressure inside the boat would have to be equalised with the external pressure first-and the hatch would push open the casing cover.
2. These arrangements were fitted subsequently to all B Class and C Class vessels. C14 was fitted about May 1909 when in hand for a permanent bridge to be installed. The position of the skirts varied between individual boats.
3. Although D1 was building at the same time as C12-16 its escape arrangements were different. An 'after conning tower' was built in way of the main motors from the pressure hull to the casing top. It was open to the pressure hull at the bottom with a balanced watertight scuttle at the top. This was the escape route. Eight airlocks of the skirt type already mentioned were fitted in way of this tower.
No airlocks were fitted forward although the arrangements for opening the forward torpedo hatch mentioned in Paragraph 1 appear to have been fitted to be used as an alternative escape route.
4. By the time D2 completed in 1911, a new type of life-saving helmet had been adopted. The after conning tower was fitted as in D1 but air-locks were deleted. The means of opening the torpedo hatch was improved being operated mechanically by handwheel through rods and gearing; the casing cover over was securely fixed by rods to the torpedo hatch. The helmets were kept in a life-saving helmet stowage in the control room with an adjacent life-saving helmet air tank for charging associated air bottles.
5. The E Class had an amidship torpedo hatch as well as a forward hatch. Both hatches were mechanically operated and an after conning tower as in the D Class was not needed nor fitted. Similar arrangements were adopted in the V Class and Nautilus and undoubtedly some other classes built during the war years.
6. With the introduction of different types of torpedo hatch the mechanical operation of these hatches ceased. The original type of diving helmet was replaced in the 1920's by the Davis Submerged Escape Apparatus (DSEA). Special escape hatches were fitted in he forward and after end compartments in Oberon (building 1924-7) but were not fitted in the Odin Class which followed.
From 1930 onwards was a period of experiment in improving the escape gear and means of escape. DSEA gear was improved and proper lockers provided for its stowage, conning towers and gun access trunks were tried as escape routes, escape chambers were introduced and eventually the 'twill trunk' was adopted.
7. It was a study of the attempts by personnel using DSEA equipment to escape from HMS/M POSEIDON, which sank in June 1931, which led to the decision to fit escape chambers in the forward and after bulkheads of the T Class. These two-man chambers were built-in as part of the bulkhead with access to and operation of the chamber from each side of the bulkhead. This was subsequently dropped in favour of the 'twill trunk'.
8. The twill trunk was about 2ft in diameter and stowed overhead under an escape hatch. In an emergency the trunk could be lowered to within a few feet of the deck. The compartment was then flooded to equalise the internal and external pressure. When the hatch was opened the twill trunk retained an air pocket in the top of the compartment in which men could breathe before donning DSEA gear and then make an escape through the trunk and hatch. It was the practice to have one escape hatch with twill trunk forward and another aft.
9. Over the years the attention paid in this country to safety appliances to assist in the location of a sunken submarine and also to assist in escape had been slight compared with some foreign navies, except in the S Class and the Swordfish (1913), both Italian designs, which were fitted with the safety appliances adopted at the time by the Italian Navy as follows:
- Safety buoys which could be released from inside the boat and, by means of attached lines, arrangements could be made for raising the vessel.
- A telephone buoy released from the control room which carried a telephone transmitter and receiver, and also a food pipe through which liquid food could be passed from the surface. The buoy in Swordfish also had an electric lamp beacon.
- The main ballast tanks could be blown from either of three positions-forward, control room or aft-so that the main tanks could be blown from either end should the control room be flooded.
- An emergency fresh air pipe extended through all habitable spaces and was always charged with high pressure air which could be released at will into any compartment, thus helping to freshen the air. By these arrangements incidentally, a damaged compartment which had become flooded might be blown out should the damage be anywhere except on top of the hull; the air release valves being operated from either side of bulkheads.
- Three divers air connections.
The above items are given as stated by Scotts the builders. Whether items (a) to (d) had ever been tried by the Italian Navy and found satisfactory in an emergency is not known.
10. In the 1920's many experiments were carried out in this country on telephone . buoys. The main difficulty was to get the buoy to 'watch' in tidal waters. A satisfactory design was eventually produced and fitted in the Rainbow Class by the time they were built. Divers air connections have been standard fittings in RN submarines for many years.
11. Progress in the development and fitting of improved arrangements for escape from and the salvage of sunken submarines may have been slower than some would have wished. At the same time there was a strong feeling by many, and this included submarine officers, that the cost, weight and complication involved was unwarranted, especially regarding salvage. The time between a submarine sinking and being located and raised ruled out salvage as a means of saving life. There is a chance, however, of escape and survival of personnel from a sunken submarine under what may be called ideal conditions when the time factor is such that the submarine has been located, a rescue vessel is present, the depth of water is not too great and too much time has not been spent by the crew in doing the natural thing of trying to get the submarine to the surface by their own efforts.
This controversial subject has been raised and studied continuously over the years. A detailed review of policy and equipment in the RN is given in a paper Escape from Submarines by H J Tabb RCNC read before the Royal Institution of Naval Architects in April 1974.
31. 2 Salvage
12. In 1905 it was decided to fit all submarines with salvage lifting eyes. A proviso was made, however, that lifting eyes were to be fitted only in those existing submarines in which an equal compensating weight could be found from existing metal ballast or removal of superstructure.
The Holland boats were each to have two lifting eyeplates. The actual number of boats fitted, if any, is not known. It was also intended that the A boats should each have four lifting eyeplates but in 1906 this was cancelled and none of the class were fitted. Weight was undoubtedly the problem.
13. In 1912 slings were made for salvage purposes. The sling consisted of two lengths of FSWR hawser with an eye at one end and the other end connected to a middle portion of FSWR sword matting. The sizes were:-
|Class||FSWR||Length of each FSWR||Length x breadth
of sword matting
|A and B||6in||6ft||12ft||20ft x 1ft|
|C||8in||7ft||13ft||20ft x 1ft 6in|
|D||9in||9ft||14ft||25ft x 1ft 9in|
|E||10 in||11ft||15ft||35ft x 2ft|
|(a) for four parallel lifts and (b) for two centre line lifts.|
The thought was to draw the slings under the submarine and hoist the boat cradled in the sword matting. Using wire rope slings in this manner was a method later employed by the USN and in principle in the case of the salvage of HMS/M Thetis.
14. The question of fitting lifting eyeplates was again seriously considered about 1930. It is thought that some boats were fitted but the practice was subsequently dropped.